THE PREVALENCE OF TUBERCULOSIS INFECTION IN NEW-SOUTH-WALES POLICE RECRUITS, 1987-1990

Objective: To determine the prevalence of tuberculosis (TB) infection and to determine the rate of conversion to a positive Mantoux test result after BCG vaccination in a subgroup of the Australian population. Design: A descriptive and retrospective study. Setting: The Police Academy, Goulburn, New South Wales. Participants: 4704 recruits to the New South Wales Police Service between 1987 and 1990. Main outcome measures: Rates of positive Mantoux test results before and after administration of BCG. Results; Eleven per cent of Police Cadets were Mantoux positive. Of those who had never been vaccinated with BCG, 7% were positive. Statistically significant differences in Mantoux positivity were found in relation to age, sex and country of birth. There was also a significant difference in the frequency of positive Mantoux reactions between the group vaccinated with BCG at the Academy and those who were vaccinated earlier in life. Conclusions: Routine Mantoux testing of population subgroups provides a useful source of information on the prevalence of TB infection. However, without testing for the ''booster phenomenon'' only a minimum estimation of the infection rate can be determined. The National Health and Medical Research Council recommendation that a Mantoux reaction of 5-9 mm be considered positive in the southern States of Australia is supported. The low rate of conversion to a positive Mantoux test result after administration of BCG vaccine at the Police Academy indicates that Mantoux testing after vaccination is not useful.